1. Field of the Disclosure
The present invention relates to touch panels, and more particularly to a touch panel which can detect a touch securely without being affected by drive of an underlying display panel and securely shield external static electricity.
2. Discussion of the Related Art
Currently, as the time turns into a full scale information oriented time, a display field in which an electric information signal is expressed in a visual sensation has been developed rapidly, and, meeting to this development, various kinds of flat display devices have been developed, which have excellent features of slimmer, lighter, and lower power consumption, to replace present cathode ray tube CRT, rapidly.
As specific examples of the flat display devices, there are the liquid crystal display device LCD, a plasma display panel device PDP, a field emission display device FED, and an electro luminescence display device ELD each of which essentially has a flat display panel in common for producing a picture. The flat display panel is provided with one pair of transparent insulating substrates bonded opposite to each other with a unique light emitting or polarizing material layer disposed therebetween.
Recently, requirements for addition of a touch panel to the liquid crystal display device are increasing for perception of a portion of the touch panel touched with a hand or additional input means and transmission of additional information matched to the touch.
Depending on touch sensing types, in the touch panels, there are a resistive type, a capacitive type, and an infrared ray sensing type, and, recently, the capacitive type is paid attention in small sized models, taking convenience of fabrication, sensing capability, and so on into account.
A related art liquid crystal display device will be described with reference to the attached drawings.
FIG. 1 illustrates a plan view of a related art touch panel, and FIGS. 2A and 2B illustrate enlarged plan views of A and B regions in FIG. 1, respectively.
Referring to FIG. 1, the related art touch panel is formed on a substrate 20 provided with an active region A/A at which touch sensing is made, and a peripheral region around the active region A/A.
Referring to FIGS. 2A and 2B, the active region A/A has a plurality of electrodes 21 formed thereon for detecting touch.
The electrodes 21 have ends having connection electrodes 30 connected thereto respectively, and each of the connection electrodes 30 has one side connected to a routing line 31 which is connected to a pad electrode 35 formed at one side of a peripheral region.
Though not shown, the pad electrodes 35 are connected to an FPC (not shown) having a touch controller which applies a signal to the pad electrodes 35.
All of the connection electrodes 30, the routing lines 31 and the pad electrodes 35 can be formed of the same material and on the same layer at the peripheral region. For an example, the connection electrodes 30, the routing lines 31 and the pad electrodes 35 can be formed of a metal having a good conductivity and a good light shielding characteristic.
Since the routing lines 31 are exposed from the substrate 20 except the pad electrodes 35 connected to the FPC and the connection electrodes 30 connected to the electrodes 21, as shown in FIG. 2B, there is no means for protecting the routing lines 31.
Consequently, at the time noise caused by external static electricity infiltrates, there is no means for shielding the noise.
And, when the touch panel is attached to a display device (not shown), such as the liquid crystal display panel, a position of the touch panel through which the routing lines 31 pass becomes to match with a circuit at the periphery of the display device, causing a problem of EMI (Electro-Magnetic Interference) taken place when the underlying display device is driven.
Thus, the related art touch panel has the following problems.
The routing lines exposed from the peripheral region of the touch panel causes noise when the external static electricity infiltrates thereto, affecting driving of the touch panel.
And, when the touch panel is attached to the liquid crystal display device, EMI interference takes place at a portion the circuit of the liquid crystal panel overlaps with the routing lines, causing malfunction of the touch.